Carpenter&#39;s tool



od. 13, 1936. B. M.' BENSEN v2,056,941;

CARPENTER S TOOL Filed May 20, 1931 2 Sheets-Sheet 1 i Y INVENTOR f MW@/UM 1 *ed* AT1-orme? Oct. 13, 1936. B M BENSEN l 2,056,948

CARPENTER S TOOL Filed May 20, 1931 2 Sheets-Sheet 2 Ber/zz M 5.012560ATTORNEY Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE CARPENTERSTOOL Bernt M. Bensen, Brooklyn, N. Y. Application May 20, 1931, SerialNo. 538,833

26 Claims.

This invention relates to tools used by carpenters in the layout of roofrafters in a frame house structure.

In the present method of determining angles and other measurementsrequired for the cutting of roof rafters, a tool or instrument, known asthe carpenters square, is commonly used. This tool is so equipped withscales and tables of dimensions as to permit a carpenter, skilled in theart of building frame houses, to determine accurately the angles andother dimensions of roof rafters. The process however is quite lengthyand requires a number of intermediate steps of calculation and thereforethe possibility of error is quite likely.

It is the object of my invention to provide a tool or instrument whichwill greatly simplify the determination of these various dimensions.

A more specific object is to provide a tool which may be set to acertain calibration indicating the lise in feet per foot of run of acommon roof rafter and from which setting the angle of plumb cut and thelength of the rafter per foot of run will both be determined.

A further object of my invention is to provide the required dimensionsfor jack, hip and valley rafters, all of which may be determined fromrespective settings of the tool to the rise in feet per foot of run.

The invention will be fully and comprehensively understood from aconsideration of the following detailed description when read inconnection with the accompanying drawings which form part of theapplication, with the understanding, however, that the improvement iscapable of extended application and is not confined to the exact showingof the drawings nor to the precise construction described and,therefore, such changes and mod iiications may be made therein as do notaffect the spirit of the invention nor exceed the scope thereof asexpressed in the appended claims.

In the drawings:

Fig. l is a side elevational View of the tool, partly broken away toshow the adjusting means.

Fig. 2 is a sectional view taken on the staggered line 2-2 of Fig. 1.

Fig. 3 is a sectional view taken on line 3--3 of Fig. 2, looking in thedirection of the arrows.

Fig. 4 is a perspective view.

Fig. 5 is a reduced side elevational view of the pivoted blade of thetool showing the face of the blade opposite to that shown in Figs. 1 and4.

Fig. 6 is a side elevational outline of a portion of the tool set todetermine the angle of plumb cut and illustrates diagrammatically thefundamental principle upon which the use of this tool in determining theplumb out is based; and

Fig. '7 is a side elevational outline view of the tool set to determinethe angle of side cut and illustrates diagrammatically the fundamentalprinciple used to determine this dimension.

Referring to the drawings for a more detailed description thereof,numeral 5 indicates the body of the tool to which is pivoted a blade 6.The body 5 comprises strips 1 and 8 parallel to each other and spacedapart. A block 9 is interposed between the strips 1 and 8 at one endthereof, screws I being employed to secure the strips 1 and 8 togetherat the mentioned end. The blade 6 is disposed between the strips 1 and 8at the other end. A pin l2, which passes thru the strips 1 and 8 andthru the blade 6, is employed to pivotally mount the blade between thementioned strips. The nut l is threaded on an end portion of the pin I2and provides a means to tighten the strips against the blade for thepurpose of temporarily holding the blade in any desired position.

A screw l1 passes nally with the strips v1 and 8. The mentioned screwcarries at its outer end a cylindrical member I8 fixed thereto. Theshoulder 20 is formed on the screw l1, said shoulder being in contactwith the inner face of the block 9 so that the screw I1 is kept frommoving in either direction longitudinally but is adapted to be rotated.Beyond the shoulder the screw I1 is threaded, this threaded portionbeing adapted to engage an interiorly threaded member 2l, said memberbeing provided with a threaded recess 22 to accommodate the mentionedscrew. The member 2l carries at an end thereof an indicator 24 whichextends upwardly and terminates in a point 25. The indicator 24 isprovided at its lower portion with a second indicator member 26 inpivotal relation to the indicator 24 and rotatable about the axis ofrotation indicated by the point 21. The exact relation between point 25and point 21 and between point 21 and member 26 will hereinafter bespecified. It will be readily understood that the indicator 24 and itsindicator member 26 may be moved longitudinally of the body of the toolby turning the cylindrical member i8.

The fundamental principles upon which the operation of this tool isbased requires certain specific limitations of proportion andconstruction. A standard unit of measurement or a fraction thereof is tobe used as the distance between certain points on the tool. Altho theinventor has chosen one inch as the preferable unit, the tool may beadapted to use any other convenient standard unit of measurement. Thedistance measured vertically between point 21 and point 25 is equal toone inch. 'I'he axial point of the pin12 is located on a theoreticalline in prolongation of the lower edge 6B of the blade 6. When the blade6 is swung downwardly and around until its upper edge 6a contacts withthe entire thru the block 9 longitudi- 20 under surface of the member26. the standard unit of one inch will again be found as the distancemeasured perpendicular to edge 6B, and between edge 6B and the point 21.The distance measuredperpendicular to the upper edge of the body 5`andthe point |2 is also one inch.

The instrument is provided with various scales,

the use of which will be hereinafter described. Y

Vnumerals 12, 24,36, e'tc.,'each major division-.be-

ing exactly one inch long, that is, the distance betweenzero pointandcalibration 12 is exactly vone inch'andlikewise the distance betweencalibrations 12 and 24 is exactly one inch. Each major division issubdivided into twelve equal parts. The member 26 functions only as anVindicatorY when the blade 6 is swung around to contact with thismember26. The point at which this indication is most desirable wouldnormally be on a line perpendicular to the longer edge of member 26indicated by numeral 26a, said perpendicular line passing thru point 21.However, the'construction of the tool makes this indicator pointinvisible'and therefore said point Yis displaced along the edge ofmember 26 an arbitrary distance to a point on member 26 where itV isvisible in actual practice one-half inch. This indicator point isdesignated by numeral25a on each face of member 26. The upper edge 6a ofthe blade 6 carries a scale 3| on Vits forward side, the zero point ofwhich would normally be on a line perpendicular to said edge'and passingthru the axis of pin I2. The displacement of the indicator point onmember 26 from its theoretical point to the point 26m beyond Vthe body 5of the tool necessitates a simi- -lar displacement of the zero pointfrom its theoretical location to a corrected point a like distance ofone-half inch. From this zero point Y the scale 3| is provided withmajor divisions spaced similarly to those specified for the scale 13|)Vand calibrated Vsimilarly to said scale 30.

These major divisions aresubdivided into twelve equal parts. The rearside of the blade 6, indicated by numeral 35, carries a scale 34 shownin Fig. 5. The function of this scale is Yto determine the angle ofplumb cut of a hip or valley rafter when said rafter lies in a verticalplane which bisects the dihedral angle defined by the-adjacent housewalls, that is, when the said rafter is positioned in a vertical planeat 45 angle'with each house wall line. It is toi be noted here that theplumb cut angle of a hip or valley rafter is determined on the basis ofthe number of inches of rise per foot of run of the common rafter in thestructure. The angle of plumb cut of the common rafter and the angle ofplumb cut of a hip or valley rafter have a certain ratiothat isequivalent to the cosine of the angle of 45. or V0.707. This, then, isthe ratio between the major divisions of scale 3| and the majordivisions of scale 34. In other words, each major division of scale 34is exactly 0.707 inches long and calibrated, as shown in Fig. 5. ThemajorV divisions of Vscale 34 are subdivided Yinto twelve equalincrements and therefore the subdivisions of scale 3| are in a ratio tosubdivisions of scale 34 as '1:0.707. The origin or In order toeliminate any possibility of misunderstanding as to the meanings ofcertain terms, a brief deiinition of these terms follows. A ridge poleis the horizontal structural member positioned at the apex of the commonrafters. AThe common rafter is a structural member placed at an anglebetween the lower roof line of the house kand the ridge pole. Hip andvalley rafters are required only when the end of a house roof isbevelled similar to the sides of the roof. Jack rafters are thestructural members positioned between the side or end of a houseroof-line and the hip rafters. The plumb cut angle is the angle betweenthe edge Yof a rafter in position and a Vertical plane. The side cutangle is that between the face of the rafter and the ridge pole measuredon a horizontal plane. This angle on common rafters is always 90. Thespecification of the pitch of a roof is generally given in terms of riseper unit of run. For example, ten inch rise per foot of run.

The use of the tool to determine the plumb cut angle of and the lengthof a Vcommon rafter is as follows. Blade 6 is swung around to the lowerside of body 5 untilY its edge 6a. contacts with the entire edge 26a ofmember 26, as shown in Fig. 6. It is assumed that the pitch of thiscommon rafter is to be a 23 inch rise per foot of run. The screw |8 isrotatedV in either direction to move the indicator 25a to register withthe tenth twenty-third subdivision on the scale 3|. The angle sodetermined between the body 5 and. the blade 6 is the angle of the plumbcut. The length of the rafter per foot of run is indicated directly onscale 30 by the indicator point 25.

The geometric derivation of these dimensions will be clearly understoodby reference to the diagrammatic triangle illustrated in Fig. 6. A linebetween points l2 and 21 is the hypotenuse c of the triangle. A linefrom point I2 projecting upwardly perpendicular to edge 6a forms thebase a of the triangle. A line from point 21 projecting upwardly andparallel to edge 6a. forms the side of the triangle. The base, side andhypotenuse of the triangle so formed are indicated respectively byletters a, b and c. Since the horizontal distance between points 2 and21 is always the fundamental unit regardless of the setting of indicator25a, and since the side b of the triangle is of a length proportionateto the rise per foot of run of a rafter, it will be observed that theangle X between the hypotenuse and this side b, that is, the'angleopposite the base a,

vbasis of the rise in feet per foot of run of the `common rafter, theblade 6 is again swung around to the position shown in Fig. 6 and theindicator point 25a is moved in either direction by turning cylindricalmember |8 until the point 25a coincides with the subdivision on scale 34which indicates the number of feet and inches of rise per foot of run ofthe common rafter. The angle of plumb cut for a hip orvalley rafter isagain that between edge 6a and the adjacent edge of the body is byreason of the previously stipulated ratio between the scale 3| and thescale 34, that is, 1:0107. The derivation of the geometric principleupon which this operation is based is similarv to that described for theplumb cut of the common rafter. In other words, the diagrammatictriangle illustrated in Fig. 6 represents the basis for this derivation.

The angle of side cut for hip and valley rafters may now be determinedfrom the same setting of the tool by swinging the blade 6 around fromits lower position Fig. 6 to that sho-Wn in Fig. 7 until edge 6B of theblade 6 contacts with the point 25. The angle thus formed between thebody 5 and the blade 6 is the required angle for the side cut of theserafters. The diagrammatic triangle shown in Fig. 'I illustrates thetrigonometric principle employed in the determination of this angle. Thebase, side and hypotenuse are designated respectively by letters d, eand f. The angle of side cut is indicated by letter Y. Since the lengthof d is proportional to the length 'of run and since the side e isproportional to the length of the common rafter, then the angle Y isdetermined from the equation e cotangent Y The length of the hip orvalley rafter is indicated directly on scale 3U where the point 25coincides with this scale. The basis for this determination is similarto that described for the length of the common rafter.

The angle of plumb cut for the jack rafters is the same as that forcommon rafters and is therefore determined in the same Way.

What is claimed as new is:

1. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a scale on said bladecalibrated in inches of rise per foot of run of a common rafter, anadjustable indicating blade stop on said body movable longitudinallythereof and adapted to limit the movement of said blade in one directionupon contact with the same and to be set relative to said scale, theangle between the blade and said body being the plumb cut angle for acommon rafter.

2. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot bein-g in line with one of said blade edges, a rst scale on saidblade calibrated in inches of rise per foot of run of a common rafter, asecond scale on said body, calibrated in inches to indicate the lengthof a common rafter per foot of run, an adjustable indicating blade stopon said body movable longitudinally thereof and adapted to limit themovement of said blade in one direction upon contact with the same andto be set relative to said first scale, the angle between the blade andsaid body being the plumb cut angle for a common rafter, the position ofsaid stop relative to said second scale indicating the length of acommon rafter.

3. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a scale on said bladecalibrated in inches of rise per foot of run of a common rafter, anadjustable indicating blade stop on said body movable longitudinallythereof and adapted to limit the movement of said blade in one directionupon contact with the same and to be set relative to said scale, theangle between the Vblade and said body being the plumb cut angle for ahip or valley rafter.

4. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having paralleledges, said pivotbeing inline with one of said blade edges, a first scale on said bladecalibrated in inches of rise per foot of run oi a common rafter, asecond scale on said body, calibrated in inches to indicate the lengthof a hip or Valley rafter per foot of run, an adjustable indicatingblade stop on said body movable longitudinally thereof and adapted tolimit the movement of said blade in one direction upon contact with thesame and to be set relative to said first scale, the angle between theblade and said body being the plumb cut angle for a hip or valleyrafter, the position of said stop relative to said second scaleindicating the length or a hip or valley rafter.

5. A tool of the character described comprising a body havin-g paralleledges, a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a scale on said bladecalibrated in inches of rise per foot of run of a common rafter, anadjustable indicating blade stop on said body movable longitudinallythereof and adapted to limit the movement of said blade in one directionupon contact with the same and to be set relative to said scale, theangle between the blade and said body being the plumb cut angle for ajack rafter.

6. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a first scale on saidblade calibrated in inches of rise per foot of run of a common rafter, asecond scale on said body, calibrated in inches to indicate the lengthof a hip or valley rafter per foot of run of a common rafter, anadjustable indicating blade stop on said body movable longitudinallythereof and adapted to limit the movement of said blade in one directionupon contact with the same and to be set relative to said scale, theangle between the blade and said body being the plumb cut angle for ahip or valley rafter. v

7. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a scale on said bladecalibrated in inches of rise per foot of run of a common rafter, anadjustable indicating blade stop on said body and movable longitudinallythereof and adapted to limit the movement of said blade and to contacteither edge of the same and tov be set relative to said scale, the anglebetween the blade and said body being the plumb cut angle for a hip orValley rafter when the blade is on one side of said body in contact withsaid stop, and the angle between the blade and said body being the sidecut angle for hip or valley rafter when the blade is on the other sideof said body in contact with said stop.

l8. A tool of the character described comprising a body having paralleledges. a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a scale on said bladecalibrated in inches of rise per foot ci run of a common rafter, anadjustable indicating blade stop on said body and movable longitudinallythereof and adapted to limit the movement of said blade and toY contacteither edge of thesame and to be se-t relative to said scale, the

`angle-between the blade and said body being the contact with said stop.

9. A tool of the-character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot Vbeing in line with one of said blade edges, a rst scale on saidblade calibrated in inches of rise per foot of run of a common rafter, asecond scale on said body calibrated to indicate the length of .a jackrafter per foot of run, an adjustable indicating blade stop on said bodyand movable longitudinally thereof and adapted to limit the movement ofsaid blade and to contact either edge of the same and to be setrelative-to said first scale', the angle between the blade and said bodybeing the plumb cut angle for a jack rafter when the blade is on oneside of said body in Contact with said stop and the .angle between theblade and said Y body being the side cut angle for a jack rafter whenthe blade is on the other side of said body in contact with saidstop,the position of saidstop relative to said second scaleindicating thelength of a jack rafter per foot of run.

V10. A tool of the character described comprising a body having paralleledges, a blade pivoted on said body and having parallel edges, saidpivot being in line with one of said blade edges, a first scale on saidblade calibrated in inches of rise per foot of run of a common rafter, asecond scale on said body calibrated to indicate the length of a hiporvalley rafter per foot of run, an adjustable indicating blade stop onsaid body and movable Y longitudinally thereof and adapted to limit themovement of said blade and to contact either edge of the same and to beset relative to said first scale, the angle between the blade andsaidbody being Vthe plumb cut angle for a hip or valley rafter when theblade is on one side of said body in contact with said stopand the anglebetween the blade and said body being the side cut angle for a hip orvalley rafter when the blade is on the other side of said body incontact with said stop, the position of said stop relative to saidsecond scale indicating the` length of a hip or valley rafter per footof run of a common rafter.

1l. A tool comprisinga scaled body portion, a scaled blade pivoted onsaid body portion and having parallel edges, an indicator movablelength- `wise of said body portion and against which either edge Vofsaid blade may contact, said indicator having ends, said indicatorhaving at one 'end a point for contact with the blade and having betweenits ends a point which is at the intersection of a line parallel to oneedge of the body portion and passing thru the pivotal point and of aline which is perpendicular to the same edge of the body portion andpasses thru said contact point, the distance from said point to one endof the indicator contacted by said blade being equal to the distancefrom said point to the far edge of the blade when the latter is swungaround to contact the other end of the indicator.

12. VA tool comprising a body having a scale calibrated in feet of riseper foot of run, a blade pivoted on said body, an indicator blade stopmovable lengthwise ofsaid body, adjacent said Scale, and adapted todetermine the position of said blade on either side of said body, saidstop being so proportioned relative to the width of the blade Aand beingso pivoted that, for a given setting of the blade stop the angle betweenthe body and the blade on one side of the body and resting against saidstop is to the angle between the body and the blade on the other side ofthe body and resting against said stop as the sine of the rst angle isto the tangent of the second angle.

13. A tool comprising .a scaled body portion, a scaled blade pivoted onsaid body and having parallel edges, an indicator movable lengthwise ofsaid body portion and against which either edge of said blade maycontact, saidindicator having ends, said indicator having at one end apoint for contact with the blade and having between its ends a pointwhich is at the intersection of a line parallel to one edge of the bodyportion ,and pass- Ving through the pivotal point and of a line which isperpendicular to the same edge of the body portion and passes throughsaid contact point, the distance from saidpoint to one end of theindicator contacted by said blade being equal to the distance from saidpoint to the far edge of the blade when the latter is swung around tocontact the other end of the indicator, the pivotal point of the bladebeing on a line with one edge of the blade.

14. A tool of the character described comprising a body, a blade pivotedon said body, the axis of rotation formed by said pivot being in linewith an edge of said blade, a scale on said blade calibrated to indicatethe rise per'foot of run of a common rafter, an adjustable indicatingblade stop on said body movable relative to said pivot and adapted todetermine the position of said blade and to be set relative to saidscale, the angle between the blade and said body being the plumb cutangle for a common rafter,

15. A tool of the character described comprising a body, a blade pivotedon said body, the axis of rotation formed by said pivot being in linewith an edge of said blade, a rst scale on said Y blade calibrated toindicate the rise per foot of run of a common rafter, a second scale onSaid body calibrated to indicate .the length of,

a common rafter per foot of run, an adjustable indicating blade stop onsaid body movable relative to said pivot and adapted to determine theangular position of said blade, and to be set relative to said firstscale, the angle between the blade and said body being the plumb cutangle l for a common rafter, and the position of said stop relative tosaid second scale indicating the length of a common rafter.

16. A tool of the character described comprising a body,` a scale onsaid body, a blade pivoted on said body, the axis of rotation formed bysaid pivot being in line with anedge of said blade, a scale on saidblade calibratedto indicate the rise per foot of run of a common rafter,an adjustable indicating blade stop on said body movable along said bodyscale relative to said pivot and adapted to engage said edge-of theblade and thus determine the angular position of said blade.

1'7. A tool of the character described comprising a body, a bladepivoted on said body, the axis of rotation formed by said pivot being inline with an edge of said blade, a rst scale on said blade calibrated toindicate the rise per foot of run of a common rafter, a second scale onsaid body calibrated to indicate the length of a hip or valley rafterper foot of run, an adjustable relative to said rst scale, the anglebetween the blade and said body being the plumb cut angle for a hip orvalley rafter, the position of said stop relative to said second scaleindicating the length of a hip or valley rafter.

18. A tool of the character described comprising a body, a blade pivotedon said body, the axis of rotation formed by said pivot being in linewith one of said blade edges, a first scale on said blade calibrated toindicate the rise per foot of run of a common rafter, a second scale onsaid body calibrated to indicate the length of a hip or valley rafterper foot of run of a common raiter, an adjustable indicating blade stopon said body movable relative to said pivot and adapted to determine theangular position of said blade and to be set relative to said firstnamed scale, the angle between the blade and said body being the plumbcut angle for a hip or valley rafter.

19. A tool of the character described comprising a body, a blade pivotedon said body, the axis of rotation formed by said pivot being in linewith an edge oi said blade, a first scale on said blade calibrated toindicate the rise per foot of run of a common rafter, a second scale onsaid body calibrated to indicate the length of a hip or valley rafterper foot of run of a common raiter, an adjustable indicating blade stopon said body movable relative to said pivot and adapted to determine theangular position of said blade and to be set relative to said firstnamed scale, the angle between the blade and said body being the plumbcut angle for a hip or valley rafter.

20. A tool of the character described comprising a body, a scale on saidbody, a blade pivoted on said body and having parallel edges, a scale onsaid blade, an indicator movable relative to the blade pivot on saidbody and against which either edge of said blade may contact, saidindicator having at one end a point for contact with the blade andhaving between its ends a point which is at the intersection of a lineparallel to one edge of the body, and passing through the pivotal pointand of a line which is perpendicular to the same edge of the body andwhich passes through said contact point, the distance from said point toone end of the indicator contacted by said blade being proportional tothe distance between the divisions of said blade scale.

21. A tool of the character described comprising a body having a scalethe divisions of which indicate the rise per foot of run of a commonrafter, a blade pivoted on said body, an indicator blade stop movablelengthwise of said body adjacent said scale and including an indicatorpoint on one side of the body coacting with the scale to determine theposition of said blade on said body, said stop extending transverselyacross the body and so proportioned relative to the divisions of saidscale so that for a given setting of the blade stop the angle betweenthe body and the blade is a trigonometric function of the length on theblade scale indicated by the stop indicator point with the blade restingagainst the end of the stop opposite the indicator point.

22. A tool of the character described comprising a body, a blade pivotedon said body and having a straight edge which if extended would passthrough the axis of the blade pivot, a blade adjustment means adapted tovary the angle of said blade, said means having a point on a lineparallel to said body and passing through said blade pivot, and having asecond point at which said blade adjustment is effective in itsengagement with said straight edge, the line passing thru both of saidpoints being constantly at a right angle to said first line.

23. A tool of the character described comprising a body, a blade pivotedon said body and adapted to be swung about towards opposite edges of thebody into either one of two operative positions, a blade adjustmentmeans adapted to vary the angle of said blade in either of said twopositions, said means having a point on a line parallel to said body andpassing through said blade pivot, and having a second point at whichsaid blade adjustment is effective when the blade is in contacttherewith, the line passing through said two points being constantly ata right angle to that longitudinal edge of said blade which contactswith the blade adjusting means.

24. A tool ofthe character described comprising a body, a blade pivotedon said body, a scale on said blade calibrated into major and mino'rgraduations, a blade adjustment means adapted to vary the angle of saidblade, said means having a point on a line parallel to said body andpassing through said blade pivot, and having a second point at whichsaid blade adjustment is effective, the line passing through both ofsaid points on the blade adjustment means being constantly at a rightangle to said first line, said points on the blade adjustment l meansbeing spaced a distance equal to one of the major divisions of saidblade scale.

25. A tool of the character described comprising a body, a blade pivotedon said body, a scale on said blade, a blade adjustment means adapted tovary the angle of said blade, said means having a point on a lineparallel to said body and passing through said blade pivot, and having asecond point at which said blade adjustment is effective, the linepassing through both of said points on the adjustment means beingconstantly at a right angle to the same longitudinal edge of said blade,said points being spaced a distance equal to one of the unit distancesof the divisions of said blade scale.

26. A device of the class described comprising a body having opposingparallel edges, a blade having opposing parallel edges and pivoted tothe body, said blade adapted to be swung about its pivot outwardly ofthe body to cause opposing edges of the blade to intersect the opposingedges of the body, meansl adjustable longitudinally of the body andprovided at opposite ends with stops against which the blade engages inits two positions to t the angles formed between the opposite edges ofthe blade and the adjacent edges of the body in the several operativeangle forming positions of the blade, a point in said means being in aline extending longitudinally of the body and passing through the axisof the blade, the ldistance between one of said stops and its coactingblade edge measured from said point with the blade in one of itspositions being equal to the shortest distance between the other stopand the same blade edge similarly measured from said point.

BERNT M. BENSEN.

